BRSTM file
BRSTM files contain ADPCM sound data. They are used for music in some games, such as Super Smash Bros. Brawl and Mario Kart Wii.
They contain a header, followed by a HEAD chunk, an ADPC chunk and a DATA chunk.
All the data in those files are big-endian, except where mentioned.
All the offsets are absolute (from beginning of file), except where mentioned.
All the sizes are in bytes, except where mentioned.
Each chunk is padded to a multiple of 0x20.
BRSTM header
The header is 64 bytes long.
| Offset | Size | Description |
|---|---|---|
| 0x0000 | 4 | "RSTM" (0x5253544D) |
| 0x0004 | 2 | Byte Order Mark (BOM), usually 0xFE 0xFF for big endian. |
| 0x0006 | 1 | Major version |
| 0x0007 | 1 | Minor version |
| 0x0008 | 4 | Size of the whole file |
| 0x000C | 2 | Header size |
| 0x000E | 2 | Number of chunks |
| 0x0010 | 4 | Offset to HEAD chunk |
| 0x0014 | 4 | Size of HEAD chunk |
| 0x0018 | 4 | Offset to ADPC chunk |
| 0x001C | 4 | Size of ADPC chunk |
| 0x0020 | 4 | Offset to DATA chunk |
| 0x0024 | 4 | Size of DATA chunk |
| 0x0028 | 24 | Unknown/Padding (zero) |
HEAD chunk
The HEAD chunk contains information about the brstm file, including sample rate, loop information, volume, panning, and information on each of the ADPCM streams.
This chunk contains 3 internal parts.
Part 1 contains general information about the file such as loop information, sample rate, and data needed to deinterleave the audio stream.
Part 2 defines the tracks in the file, and contains volume and panning information for each of them.
Part 3 contains the information needed to decode the ADPCM audio, including the ADPCM coefficients, and history samples.
Any offsets in the HEAD chunk are relative to offset 0x08 in the HEAD chunk unless otherwise noted.
Header
| Offset | Size | Description |
|---|---|---|
| 0x0000 | 4 | "HEAD" (0x48454144) |
| 0x0004 | 4 | Length of entire HEAD section. |
| 0x0008 | 4 | Marker? (0x01000000) |
| 0x000C | 4 | Offset to HEAD chunk part 1 |
| 0x0010 | 4 | Marker? (0x01000000) |
| 0x0014 | 4 | Offset to HEAD chunk part 2 |
| 0x0018 | 4 | Marker? (0x01000000) |
| 0x001C | 4 | Offset to HEAD chunk part 3 |
HEAD chunk part 1
This part is 0x34 bytes long
| Offset | Size | Description |
|---|---|---|
| 0x0000 | 1 | Codec:
0 - 8-bit PCM |
| 0x0001 | 1 | Loop flag |
| 0x0002 | 1 | Number of channels |
| 0x0003 | 0 | Padding? (0x00) |
| 0x0004 | 2 | Sample rate |
| 0x0006 | 2 | Padding? (0x00) |
| 0x0008 | 4 | Loop start in samples |
| 0x000C | 4 | Total sample count |
| 0x0010 | 4 | Absolute offset to the beginning of the ADPCM data.
Note that this is not the beginning of the DATA chunk. |
| 0x0014 | 4 | Total block count.
The total number of interlaced blocks in the ADPCM data. This count includes the final block. |
| 0x0018 | 4 | Block Size in bytes. |
| 0x001C | 4 | Samples per block. |
| 0x0020 | 4 | Size of the final block without padding in bytes |
| 0x0024 | 4 | Samples in the final block. |
| 0x0028 | 4 | Size of the final block with padding in bytes |
| 0x002C | 4 | Samples per entry in the ADPC table |
| 0x0030 | 4 | Bytes per entry in the ADPC table |
HEAD chunk part 2
Header
| Offset | Size | Description |
|---|---|---|
| 0x0000 | 1 | Number of tracks |
| 0x0001 | 1 | Track Description Type |
| 0x0002 | 2 | Padding? (0x00) |
Offset table
The header contains one of this structure for each track
| Offset | Size | Description |
|---|---|---|
| 0x0000 | 1 | 0x01 |
| 0x0001 | 1 | Track description type |
| 0x0002 | 2 | Padding? (0x00) |
| 0x0004 | 4 | Offset to track description |
Track Descriptions
There are at least 2 known types of track descriptions:
| Type | Description |
|---|---|
| 0 | Used in Super Smash Bros. Brawl |
| 1 | Used in other games. |
The header contains one track description for each track
Track Description Type 0
| Offset | Size | Description |
|---|---|---|
| 0x0000 | 1 | Number of channels in track |
| 0x0001 | 1 | Left channel ID if stereo track. Only channel if mono. |
| 0x0002 | 1 | Right channel ID if stereo track. 0x00 if mono. |
| 0x0003 | 1 | Padding? (0x00) |
Track Description Type 1
| Offset | Size | Description |
|---|---|---|
| 0x0000 | 1 | Track volume (0x00 to 0x7F) |
| 0x0001 | 1 | Track panning (0x00 to 0x7F, Left to right) |
| 0x0002 | 2 | Padding? (0x00) |
| 0x0004 | 4 | Padding? (0x00) |
| 0x0008 | 1 | Number of channels in track |
| 0x0009 | 1 | Left channel ID if stereo track. Only channel if mono. |
| 0x000A | 1 | Right channel ID if stereo track. 0x00 if mono. |
| 0x000B | 1 | Padding? (0x00) |
HEAD chunk part 3
Header
| Offset | Size | Description |
|---|---|---|
| 0x0000 | 1 | Number of channels |
| 0x0001 | 3 | Padding? (0x00) |
Offset table
The header contains one of this structure for each channel
| Offset | Size | Description |
|---|---|---|
| 0x0000 | 4 | Marker (0x01000000) |
| 0x0004 | 4 | Offset to channel information |
ADPCM Channel Information
The header contains one of this structure for each channel.
| Offset | Size | Description |
|---|---|---|
| 0x0000 | 4 | Marker (0x01000000) |
| 0x0004 | 4 | Offset to channel ADPCM coefficients |
| 0x0008 | 0x20 | 16 Int16 ADPCM coefficients |
| 0x0028 | 2 | Gain |
| 0x002A | 2 | Initial predictor/scale |
| 0x002C | 2 | History sample 1 (Sample - 1) |
| 0x002E | 2 | History sample 2 (Sample - 2) |
| 0x0030 | 2 | Loop predictor/scale If BRSTM doesn't loop, these will be the same as the initial predictor/scale and history. |
| 0x0032 | 2 | Loop History sample 1 (Sample - 1) |
| 0x0034 | 2 | Loop History sample 2 (Sample - 2) |
| 0x0036 | 2 | Padding (0x00) |
ADPC chunk
The ADPC chunk contains 2 PCM history samples per channel for every entry in the table.
The number of samples per entry is specified in the HEAD chunk.
Each entry in the table contains the final two samples from the preceding block.
The first entry in the table contains the history samples contained in part 3 of the HEAD chunk.
Header
| Offset | Size | Description |
|---|---|---|
| 0x0000 | 4 | "ADPC" (0x41445043) |
| 0x0004 | 4 | Length of entire ADPC section. |
ADPC table entry
The size of each entry is the channel count * 4
| Offset | Size | Description |
|---|---|---|
| 0x0000 | 2 | Channel 0 History sample 1 |
| 0x0002 | 2 | Channel 0 History sample 2 |
| 0x0004 | 2 | Channel 1 History sample 1 |
| 0x0006 | 2 | Channel 1 History sample 2 |
| ... | 2 | Channel N History sample 1 |
| ... | 2 | Channel N History sample 2 |
DATA chunk
The DATA chunk contains ADPCM sound data.
Header
| Offset | Size | Description |
|---|---|---|
| 0x0000 | 4 | "DATA" (0x44415441) |
| 0x0004 | 4 | Length of entire DATA section. |
| 0x0008 | 4 | Number of padding samples between header and ADPCM data? Always 0x18 |
| 0x000C | 0x14 | Padding (0x00) |
ADPCM Data
The ADPCM audio data is interlaced per channel according to the block sizes specified in the header.
| Description | Size |
|---|---|
| Channel 0 block 0 | Block size |
| Channel 1 block 0 | Block size |
| Channel 0 block 1 | Block size |
| Channel 1 block 1 | Block size |
| ... | |
| Channel 0 final block | Final block size |
| Channel 1 final block | Final block size |